Hello,every body,can u help me ?

[coredump]

blackadder wrote:

The Commodore 64 did something like this, they took 9VAC from the power supply and ran it through a schmitt trigger to create 60Hz clock pulses for the 6526 TOD counter.

Which is fine until you run your code on a Commodore 64 in Europe and the interrupts come in at 50Hz. Did the C64 ROM correct for this somehow? I know I had a non-volatile real-time clock add-on for the Atari ST that came with clock software that assumed a 60Hz clock and ran slow on 50Hz mains.

[blackadder]

coredump wrote:

Which is fine until you run your code on a Commodore 64 in Europe and the interrupts come in at 50Hz. Did the C64 ROM correct for this somehow? I know I had a non-volatile real-time clock add-on for the Atari ST that came with clock software that assumed a 60Hz clock and ran slow on 50Hz mains.

The TOD clock in the 6526 CIA apparently has a setting for 50/60Hz.
Of course doing a clock using the power line freq for interrupts you wouldn't have this luxury. As long as you only want time to the second it's just a matter of counting pulses and incrementing the clock every 50 or 60 counts.


BTW, you can see the schmitt trigger circuit here, it's at the bottom of sheet 2.
http://www.devili.iki.fi/Computers/Comm ... Schematic/